Apparently over 31 million prescriptions for antidepressants were handed out by doctors in Britain in 2006 which represents a six per cent increase from 2005.

This figure includes a ten per cent rise in the prescribing of SSRIs (Serotonin Specific Reuptake Inhibitors) such as Prozac by local doctors.

The figures are a concern and a leading mental health charity in the UK says that instead of relying solely on drugs people should also receive ecotherapy.

This advice comes as a result of a new study funded by the charity MIND.

The study by researchers at the University of Essex tested the impact of a 30-minute walk in a country park with a walk in an indoor shopping centre on a group of 20 members of local Mind associations.

The researchers found that in 71 per cent of people with mental health problems, going for a walk decreased levels of depression and left them feeling more relaxed, while a further 90 per cent had increased self esteem.

This was in stark contrast to only 45% who experienced a decrease in depression after the shopping centre walk, where 22% said they actually felt even more depressed.

As many as 50% also said they felt more tense and 44% said their self-esteem had dropped after window-shopping at the centre.

The so-called 'green treatment' involves walking, kite-flying and gardening and the charity says it should be recognised as a clinically-valid frontline treatment for mental health problems.

Paul Farmer, the chief executive of MIND says it is not suggested that ecotherapy should replace drugs, but the debate on its use "needs to be broadened".

The charity has also called for care farms where patients are prescribed agricultural work as a treatment for mental distress.

Mr Farmer says MIND considers ecotherapy to be an important part of the future for mental health; he says it is a credible, clinically-valid treatment option and needs to be prescribed by GPs, especially when for many people access to treatments other than antidepressants is extremely limited.

Mr Farmer says hundreds of people have benefited from the green projects run by local Mind associations but if prescribing ecotherapy was part of mainstream practice it could potentially help the millions of people across the country who are affected by mental distress.

In a second study the researchers asked 108 people with various mental health problems about their experiences of ecotherapy and 94% said green activities had benefited their mental health and lifted depression while 90% said the combination of nature and exercise had the greatest effect.

Mind describes ecotherapy as "getting outdoors and getting active in a green environment as a way of boosting mental well-being".

It is estimated that one in four people in Britain has a form of mental illness.